In general, longitudinal frame members that extend in the longitudinal direction of a vehicle are provided on both sides of a front compartment in the lateral direction of a vehicle, that is disposed on a front portion of the vehicle body. For example, in a unitized body, a rear portion of a front side member, comprising the longitudinal frame members, extends in the rear direction and the frame members are offset (shifted) downwardly from kick-up portions (buckling points) relative to the front part. (See Laid Open Japanese Patent No. 2004-75021.)
When a collision load is applied to the front side member during a frontal collision of the vehicle, the front portions are bent and deformed upwardly around the kick-up portions, thereby absorbing the collision energy.
However, in the above-mentioned conventional body frame structure, the front portions of the longitudinal frame members are bent and deformed upwardly around the kick-up portion during a frontal collision, and therefore, in order to secure the predetermined amount of collision energy absorption, the bent deformation displacement of the front portions of the longitudinal frame members in the rear direction should be secured. The longitudinal dimension of the front compartment becomes longer, and consequently the auto body becomes longer.